Multiple light-flash-producing system



Feb. 19, 1957 H. E. EDGERTON 2,781,707

MULTIPLE LIGHT-FLASH-PRODUCING SYSTEM Filed Sept. l2, 1952 v 2 Sheets-Sheet 2 INVENTOR. jfl/@0m E. 5065/9704/ www ATTOPZVEYS United States Patent MULTIPLE LIGHT-FLASH-PRODUCING SYSTEM Harold E, Edgerton, Belmont, Mass. Application September 12, 1952, Serial No. 309,307

I 17 Claims- C1 9.5-1.1)

The present invention relates to multiple light-flashproducing systems and more particularly, to apparatus in which 'light flashes of duration of theorder of a microsecondor less are produced at intervals of the order of microseconds.

It has heretofore been proposed, as in my prior United States Letters Patent No. 2,186,013, issued January 9, 1940, to utilize a repetitively discharged flash tube for producing successive light flashes, say of lAMOO of a second duration, that enable the photographing of objects in motion or other phenomena occurring at` high speeds. Such devices are entirely satisfactory for many applications of multiple flash photography. It is sometimes required, however, that the light flashes be o f much briefer duration, say of the order of a microsecond or afraction thereof, and that the flashes occur once every microsecond or every few microseconds. lft is not physically possible to operate such flash-tube apparatus, however, to produce such short and rapidly occurring light flashes because the flash condenser that discharges through the flash tube cannot successively charge to itsnecessary high voltage value in such short time intervals.

{Adf'object of the present invention, therefore, is to provide a new and improved electrically operated light-flashpproducing system that, while of more general utility, is particularly adapted for producing microseconl light ilashesat intervals of the order of microseconds. i `I'naccordance with a feature of the invention, this end is achieved through the use of a plurality of successively operated discharge devices. While it has heretofore been propesed to utilize a plurality of flash lamps energized in sequence by successively dischargedlashingcondensers, this has! besa fer. the.. Purpose, Qf'providinga moving, light beatrfas for beacons.A A system of thisv character is de-- scribed, yfor example, in my prior United Statesy Letters Patentfh2,fl7'it,908, issued August 16,` 1949; Sucha system,` however, does' not provide successive light flashesemanating fromv aJ fixed soureeas may be required for multipleashphotosraphv,

Afurther' object of the present invention is to provide a multiple light-flash-producing apparatus that will produce successive light vflashes atea common fixed point. Thisis achieved, accordancewith a preferred embodiment of the invention, by connecting a single flash tube in the discharge circuits of all of the plurality .discharge devices andsequentially producing successive triggering voltages for accurately producing shortdischarges inv-the successive discharge devices in order successively tollash theilash tube.

An additional object of the invention is to provideA a. new'and improved photographic apparatus utilizing such a multiple light-ash-producing system.

Other and further objects willjbe elqrlainedV hereinafter and `will be more particularlypointedl out in the appended claims.

The. invention will nowfble .more fully .describedin con;-Y esctiea .with the aseompanyirladrawiass Fis 1' Qfrwhich is a schematic view illustrating the multiple light-Hashmi 2,78l,707 C@ Patented Feb. 19, 1957 il producing apparatus of the present invention applied to silhouette photography; and

Eig. 2 is a schematic circuit diagram of a preferred multiple light-ash-producing circuit for use in the system of; Fig. 1f.

yln Fig. 1, a multiple light-ash-producing circuit 1 Ais shown energizing the lprincipal electrodes 3 and 5 of a flash tube o r lamp 7, the details of which will hereinafter be described. The light produced from the flashes of the tube 7 is focused by a Fresnel field lens, as of plastic, upon the lens 9 of a photographic camera 11. The lens 9 may be stopped down by a conventional diaphragm, not shown, without a loss of light on the camera film, also not shown, if the image of Athe flashes does not ll' the camera lens 9.

Lf itis desired to obtain silhouette photographs, as s-rnall an aperture as possible should preferably be used at the lens 9 to exclude light from the subject to be photographed. This subject is shown, for illustrative purposes, as an explodable dynamite cap 13, energizable by conductors 15, but it may comprise any other rapidly moving object. Though the successive light flashes of' the lalljp 7- are focused on the camera lens 9, producing outof-focus images of the light flashes on a substantial' area ofthe film, the image of the subject 13 is focused upon the camera film so that successive shadows of the subject 13 are photographed.

If, on the other hand, it is ldesired to produce normal photographs of the subject instead of silhouettes, the same equipment may be used to produce ample light forreflected-light photography. It is merely necessary to directv the light flashes upon the subject 13 and to focus the light reflected from the subject 13 upon the photographic film of the camera l1. The system may also be adapted for the production of Schlieren-type photographs, inI which case the image of the light ashes produced by the flash tube 7 should be deflected so that only a portion of: the light goes into the camera lens 9, as is well known.

The taking of the photographs may, if desired, be syn; chronized with the behavior or operation of the subject. In theV case of subjects that emit their own light, such as the explodable subject 13, the illumination from` the subjectmay energize a photocell 17 that, in turn, may initiate the operation of the multiple light-flash-producing circuit 1.

Assuming for the moment` that light flashes are producedl by the system 1-7 of duration of the order ofa function of a microsecond, spaced a time irltervaly of the order of amicrosecond or two, successive shadow, re-

flected-light, Schlieren-type or other photographs may,`

thus be produced `upon the camera film to demonstrate the pri-)grossy of the explosion of the subject 13 at these short successive intervals `of time. Suchphotographs may be used to determine the velocity of the explosion and various other details concerning the explosive process. The invention, of course, as before started, may ybe used with other subjects than explodable subjects, isuch as -a subject moving at a ri-gh rate of speed and the motion of which it is desired to study over very brief intervals voftime of the order of microseconds.

I n the preferred circuit arrangement of Fig. 2, the

' muptiple light-fiash-producing system 'isshown compris,-

ing circuits for producing a pair of successive fractional= nii'c'rosecond light-flashes, spaced a few microseconds apart. lt is' to be understood, however, that additional flash-producing circuits of this same character may be employedand that the invention is not limited to thepuse of circuits for producing but two flashes. Thel two-flash system has particular application in connection with the study of the before-discussed explodable dynamite caps alla-fh@ like- Basically, the system 1 comprises a pair of dischargev devices 2 and 4 through which successive discharges are passed in order to effect the successive dashing of the tube 7. A iirst trigger device, shown as a gaseous-discharge tube 19. as of the thyratron type, is connected with the photocell 17 to produce a first trigger pulse in a trigger transformer 21 that caulses the discharge through the discharge device 2 land thus produces a iirst flash of light in the tube 7. The illumination produced in the photocell 17 by the explosion of the subject 13 thus initiates the operation of the multiple-ash-producing system 1. A time-constantcontrolled electric network, generally indicated by the reference numeral 6. connects the thyratron trigger device 19 to a second similar trigger device 23 for delaying the production of a second trigger pulse in a second trigger transformer 25 a few microseconds after the production of the first liash of light in the flash tube 7. This delayed trigger pulse in the transformer 25 triggers the second discharge device 4 and thus produces a second flash of light through the tiash tube 7 a time interval `of the order of microseconds after the first ash of light.

The discharge devices 2 and 4 may themselves be used as the light-producing sources, in which event the flash device 7 will not be needed. Such operation. however, reuuires that the successive light flashes originate from different positions or locations. Where this is unobiectionable. such a svstem may be used. Where. however, it is desired that the light flashes emanate from the same fixed single location, as in the system of Fig. l, the liash tube 7 is employed.

The flash devices 2 and 4 are preferably in the form of spark-gap three-electrode elements having respective principal electrodes 8, 10. and 11, 12, and trigger electrodes 16 and 18. As before stated in connection with the prior-art multiple flashing systems. it would not be possible to utilize a single spark-gap for producing the closely spaced short-duration pulses involved in the present invention in view of the phvsical limitations on the rapid successive charging and discharging of the same flash condenser through the spark-gap. Instead, it is necessary to provide a separate liash condenser for each of the discharge devices 2 and 4 and simultaneously to charge the iiash condensers. The flash condenser 27 is shown connected between the principal electrode 8 and. through the resistors 31 and 29, the principal electrode 10 of the discharge device 2. The flash condenser 33 is similarly shown connected between the principal electrode 12 and,

through the same resistor 31 and a further resistor 35, the principal electrode 11 of the discharge device 4. The condensers 27 and 33 are simultaneously charged in parallel paths in the circuits traceable from the terminal labelled H. V.- through respective charging resistors 37 and 39 to a common terminal labelled H. V.l. The H. V.-l terminal is the positive terminal of a high-voltage source of direct-current energy which may, for example, be of the order of 8 kilovolts, and the terminal H. V.- is the negative terminal of the source, H. V.+ being shown preferably grounded at 41. Before the application of'a stimulus to their trigger electrodes 16 and 18, the discharge devices Zand 4 are held non-conductive, :so that they normally can not discharge the energy of the respective charged condensers 27 and 33.

The thyratron trigger device 19 for rendering the discharge device 2 conductive has an anode 59, a control electrode 51 and a cathode 53. Anode voltage is supplied through a load 61 and a series resistor 45 from the .B-lor positive terminal of the thyratron plate-supply voltage source which is of considerably lower voltage value than the H. V. source. The cathode 53 is connected through a resistor 55 to the ground terminal 41 that, in turn, forms the junction of the plate-supply bleeder network resistors 71 and 69. A plate-supply condenser 67 shuts the resistor 71. The B or negative terminal of the thyratron plate supply source is connected to the lower terminal of the resistor 69 and, in turn, applies a negative cut-off bias on the grid 51 of the thyratron 19 through a resistor 6 3. The thyratron 19 is thus initially non-conducting. The thyratron 23 is similarly initially non-conducting as a result of the application of this negative bias from the B- terminal through a resistor 89 and ya. further resistor 79 to its control electrode 81. The anode 87 of the thyratron 23 is connected to the B+ terminal in parallel with the `anode 59 of the thyratron 19 through a load 89 and the series resistor 45. The cathode of the thyratron 23 is connected directly to the ground terminal 41.

Between the anodes and cathodes of the thyratrons 19 and 23 are connected storage condensers in series with the left-hand or primary windings of the respective transformers 21 and 25. The storage condenser 57 is connected through the primary winding 32 of the transformer 21 between the anode 59 and the cathode 53 of the thyratron 19 and becomes charged during the quiescence of the thyratron 19 from the B-lplate supply, through resistors 45 and 61, 55 and 69. The storage condenser 91 is similarly simultaneously charged through the resistors 45, 89 and 69 since it is connected through the primary winding 36 of the transformer 25 between the anode 87 and the cathode 85 of the normally nonconductive thyratron 23.

Upon the emission of illumination by the explodable subject 13 and the impingement of the. illumination upon the photocell 17, a positive voltage is applied to the con trol electrode 51 of the thyratron 19 to render the same suddenly conductive. This positive voltage results from the conduction of the photocell between its anode 43 and cathode 47, completing or closing a normally open circuit traceable from the B-lterminal through resistor 45 and by way of conductor 20 to the photocell anode 43, thence through the photocell 17 to its cathode 47, and by conductor 22 and through resistor 65 to the B- terminal. The upper terminal 24 of the resistor 65 is thus rendered positive and a positive triggering voltage is applied through condenser 49 to the control electrode 51 of the thyratron 19. The condenser 57 then rapidly discharges in an oscillatory discharge circuit comprising the primary Winding 32 and the conducting tube 19, and the time constants of which are chosen so that the halfperiod of the oscillations of the di-scharge corresponds preferably to a microsecond or so, or a fractional part thereof. The subsequent half-cycle of the oscillation cuts oft the thyratron by rendering its anode 59 negative with respect to the cathode 53, so that a desired microsecond trigger impulse is impressed in the secondary winding 34 of the transformer 21. As an illustration.' with a condenser 57 (and 91) of about 0.01 microfarad and they hereinafter described transformer windings 21 (and 25), pulses of the order of a lifth to a half micro, second have been produced in the secondary winding of the transformer. This trigger pulse is in turn im? pressed from the secondary Winding 34 by way of con-l ductor 73 and through a' coupling condenser 75 upon the trigger electrode 16 of the discharge gap 2, render! ing the same rapidly conductive. The condenser 27 then discharges through the conductive gap 2 between the principal electrodes 8 and 10. To insure timing accuracy, the voltage pulses from the trigger transformer 21 (and 25) must rapidly rise to ample voltage value for triggering the gap 2 (and 4) promptly. The transformers used for such purpose may, for example, have a 1to15 primary-to-secondary winding turns ratio on a closed core. The secondary-winding voltage may, for example, reach 10 kilovolts in about 1 microsecond, and the trigger gap 2 (and 4) may tire in less than half of a microsecond.

inasmuch as the electrodes 3 and 5 of theiiash or spark-discharge tube 7 are connected across the load resistor 31, a flash or spark is produced between the electrodes 3 and 5 in response to the discharge through the discharge gap 2, and a rst light Hash of duration of epreuve? the order :of a lrnic'rosecond for :a fractional part thereof is rproduced.

The 'circuit inductance in the discharge circuit of Lthe spark-,gap condenser 27 (and 33) is :preferably reduced vto a minimum `since the 'frequency :of :oscillations vof'the discharge determines the maximum frate 'Sat which energy can be discharged into the gap. The gaps of Ithe discharge device 2 (and 4) Shave negligible resistance and `therefore appropriate `substantially Vcritical damping resistance yis required vto prevent `the 'circuit from oscillating. Normally such an'und'ampe'd low-inductance circuit will oscillate about 1'0 cycles before thej-'unplitude `is down to one-third of its initial value, 'so that critical damping is essential to maintaining the vdesired microsecond or fractional Arnicro-secimd ash duration. The critical damping resistance R is related to the capacitance C of the condenser 27 or 33 and the frequency 'f of oscillations -as follows:

L nrCf With a condenser V27 ,(o`r33) of value about 0.0.05X1'0ro farads, for example, and a frequency .of discharge-oscillations of 3)(106 cycles, the damping .resistance calcu- .lates to about 20 ohms. This 20-ohm critical Vdamping resistor is the resistor 29 (o1-'the resistor 35). `In actual practice, a `somewhat lower resistance value may be used, and some of the oscillations Vmay be toleratedin consider-ation of the possible reduction in Vlight output. The resistor 31, however, common to the Vv'gap-discharge circuits ofboth Athe gaps 2 and "i, is relatively high, say, of the order of 1()5 ohms, and it must be capable of taking the before-mentioned illustrative `8kiilovolt dis'- charge Vvoltage produced 'thereacross A Vhigh-voltage type of resistor should therefore be utilized. The a-sh or spark tube 7 itself 'may 'comprise 40 .mil nickel wire terminals connected Ato the pair Y'of preferably rounded electrodes 3 and 5 spaced in air 'about one-eighth of an inch. It has been found that erratic Aperformance can be `minimized through the rounding of the electrodes and ythat consistent Vstarting without time jitter can be achieved through the use of aglass tube 7 fitting closely about the electrodes 3 and vk5 to bridge the gap.

Accompanying the rendering conductive o'f the 'thyratron 19 is Athe sudden -'rising of the potential upon yits 'cathode 53. Were Vthis ycathode directly connected tothe control electrode 'Si of the thyratron 23, this sudden potential rise would render the thyratron Z3 rapidly conductive and effect the triggering of the "spark gap 4. 'It is V:desired Vas 'before explainedphowever, to delay ythis 'triggering van interval of time of the order of Va microsecond or a few microseconds. VTo this end, the beforementioned delay circuito Vis connected between the cathode 'S3 of the thyratron `1'9 and the control electrode 81 of the thyratron 23 to delay the conduction of the second thyratron 23. The'delay Acircuit-6 is illustrated as altimecons`tant-controlled electric network comprising a variable resistor 77 connected between the cathode 53 of the thyrat-ron 19 and, through a further resistor 79, the control electrode '31 of `the thyratron 23, and a condenser "83 connected from the 'junction of the resistors 77 and 79 lto the ground termi-nal 41. `When the cathode 5'3 suddenly becomes positive -in response to the conduct-ion of the thyration i9, this positive impulse passes through the `resisto-r 77 and condenser charging 'the condenser '83 positively 1in a .time dependent upon the time con.- Vstant of ythese elements. This time may be yvaried by varying the value .of the resistor 77. It may, for example, `be adjusted to :a value of the order of one to three microseconds, or to any other desired short time interval. Upon the positive vcharging of the condenser S3, the grid 81 to .which the .condenser 83 :is connected through kthe resistor' 79 becom-es positive, also,v and the thyratron 23 suddenly conducts. The condenser 91 rapidly discharges through the primary Vwinding 3'6. of the 'transformer' 25 andthe conducting thyratron 23, Fas discussed .in foon.- -nection withthedischarg'e of the condenser157, producing thedesired'short triggering impulse in the'secondairytvinding 3S. This triggering impulse in the secondary winding 38 of the transformer 25 is fed'byconductor -93fthrough a coupling condenser 9'5 to the trigger electrode 518 'ofthfe discharge 'device 4. The .discharge gap '4 'thus is rapidly triggered to discharge `the voltage :of the condenser $3 therethrough and thus to lproduce a voltage pulseacross the resistor 31 that again dashes the tube 7. This further flashing of the tube 7 occurs, moreover, a Ztme'atcrIhe first flashing of the `tube 7 in-response to the 'discharge of the trigger gap 2, that corresponds to 'thetime-de'layfsetting of thetirne-delay circuit 6, namely, a microsecondlor a few microseconds 'in the example above discussed. .The resistors 96 maintain the trigger electrodes 16 and '18 at the potential Yof the respective principal v'electrodes 18 -and 12 before the discharges.

It has been found that the ashintensity .produced iby the discharge of the second ydischarge-'gap vcondenser -33 is generally, in practice, `somewhat less thantha't .produced "by the discharge :of the condenser 27, even Ythough 'the condensers are simultaneously charged from the same H. V. source. In order to produce successive light flashes from the tube 7 that are of equal ash intensity, therefore, Vit yis desirable to `increase the value of the second discharge-gap condenser 33. In one apparatus, for example, the value of the condenser '33 was made two times the value of the condenser 27 in order to produce suc- :ccssive light flashes of substantially equal light intensity.

As an illustration of a practical yapplication of the circuit of Fig. 2 to the system of Fig. l, `the shockwave lof La bursting dynamite cap .13 has been photographed with one-fifth microsecond -pulses delayed about .four microseconds apart. During this time, the VVshock wave of the dynamite cap moved about 0.4 inch and 'the average velocity over this time interval was found from the silhouette photographs to be 'about 0.1 inch per micro- `second or about 8000 feet per second.

If it is desired to initiate the triggering of 'the device 1 by other than an object that emits light, instead of the phfotocell 17, a push button conrol 97 may be utilized that grounds the contr-ol electrode Sfr of the thyratron 1'9 and vthus causes the thyratron 19 to conduct' and discharge the condenser 57 therethrough, setting off the multiple-'dash system. Other well-known types of trigger devices than thyratrons may yalso be employed, as may other types of discharge devices 2 and 4 and flash devices 7, 'though the described arrangement has been found to produce very satisfactory results. Similarly other types of delay systems 6 may be employed such as a length of coaxial Aline for .a xed delay, or more precise time-constant coupling circuits.

Further'modiications will occur to those skilled 'in the art and all such are considered to fall within the spirit and scope of the invention, as defined in the appended clainis.

What is claimed is:

l. Alight-dash producing system having, in combination, a plurality of condensers, a plurality-of normally non-conductive discharge devices through which electric energy may discharge when conductive, one discharge Idevice corresponding to each condenser, a discharge circuit connecting each condenser `to its corresponding discharge Idevice :to lenable 'the discharge `of the electric venergy charged in the condenser through its corresponding discharge device when the discharge device is rendered conductive, the discharge circuits sharing a common load impedance, means for charging each condenser, 'means for applying successive triggering voltages to the successive discharge devices to render the discharge devices conductive rapidly in predetermined sequence in order thereby to permit the yciischarg'e of the condense'rs through ,their cor-responding discharge devices rapidly in the said predetermined sequence, vand a common ash lamp connected to the common load impedance of the discharge circuits of the discharge devices and responsive rto the discharges of electric energy therethrough for producing light ilashes rapidly in -the said predetermined sequence at the single location of the flash lamp.

2. A light-ash-producing-and-recording system having, in combination, a plurality of condensers, -a plurality of normally non-conductive discharge devi-ces through which electric energy may discharge when conductive, one discharge device corresponding to each condenser, a discharge circuit connecting each condenser to its corresponding discharge device to enable the discharge of the electric energy charged in the condenser through its corresponding discharge device when the discharge device is rendered conductive, the discharge circuits sharing a cornmon load impedance, means for charging each condenser, means for applying successive triggering voltages :to the successive discharge devices to render the discharge dcvices conductive rapidly in predetermined sequence in order to discharge the condensers through their corresponding discharge devices rapidly in the said predetermined sequence, a common flash lamp connected to the common load impedance of the discharge circuits of the discharge devices and responsive to the discharges of electric energy therethrough for producing light ashes rapidly in the said predetermined sequence at a single location, and a field lens for focusing the light flashes produced by the ash lamp upon a camera lens in order to form an out-of-focus image of the flash lamp upon a substantial area of the camera lm, thereby to produce rapid shadow exposures upon the lm in lthe said predetermined sequence of an .object located between the eld ylens and the camera and focused upon the lm.

3. A ligh't-flash-producing system having, in combination, a plurality lof condensers, a plurality of normally non-conductive discharge devices through which electric energy may discharge when conductive, one discharge device corresponding `to each condenser, a discharge circuit connecting each condenser to its corresponding discharge device to enable the discharge of the electric energy charged in the condenser through its corresponding discharge device when the discharge device is rendered conductive, means for charging each condens-er, means for rendering the discharge devices conductive rapidly in predetermined sequence to discharge the condensers through their corresponding discharge devices rapidly in the said predetermined sequence, a common load connected in all of the discharge circuits of the discharge devices, and a ilash lamp connected to the load and responsive to the discharges yof electrical energy through the discharge circuits for producing light flashes rapidly in the said predetermined sequence at the single location :of the dash lamp.

4. A light-flas'h-producing system having, in combination, a plurality of condensers, a plurality of normally non-conductive discharge gaps through which electric energy may discharge when conductive, one discharge gap corresponding to each condenser, a discharge circuit connecting each condenser to its corresponding discharge gap to enable the discharge of the electric energy charged in the condenser 4through its corresponding discharge gap when the discharge gap is rendered conductive, means for charging each condenser, a plurality of normally ineffective trigger devices, one corresponding to each discharge gap, for rendering the corresponding discharge gaps conductive when effective, and means for rendering the trigger devices etfect-ive rapidly in predetermined sequence Vto render the corresponding discharge ygaps conductive rapidly in :the said predetermined sequence, there-by to discharge the condensers through their corresponding discharge gaps rapidly in the said predetermined sequence, a common load connected in all of the discharge circuits of the discharge gaps, and a ash lamp connected to the load and responsive to the discharges of electric energyl through the discharge circuits for producing light flashes rapidly in the said predetermined sequence at the single location of the flash lamp.

5. A light-ash-producing system having, in combination, a plurality of condensers, a plurality of normally non-conductive discharge gaps through which electric energy may discharge when conductive, one discharge gap corresponding to each condenser, a discharge circuit having little inductance and critically damped connecting each condenser to its corresponding discharge gap to enable the discharge of the electric energy charged in the condenser through its corresponding discharge gap when the discharge gap is rendered conductive, means for charging each condenser, a plurality of normally ineffective trigger devices, one corresponding to each discharge gap, for rendering the corresponding discharge gaps conductive when effective, and means for rendering the trigger devices effective rapidly in predetermined sequence in order to render the corresponding discharge gaps conductive rapidly in the said predetermined sequence, thereby -to discharge the condensers -through their corresponding discharge gaps rapidly in the said predetermined sequence, a common load connected in all of the discharge circuits of the discharge gaps, and a iiash lamp connected to the Iload and lresponsive to the discharges of electric energy through the discharge circuits for producing light ashes rapidly in the said predetermined sequence lat the single location of the flash lamp.

6. A light-ash-producing system having, in combination, a plurality of condensers, a plurality of normally non-conductive discharge gaps through which electric energy may discharge when conductive, one discharge gap corresponding to each condenser, a discharge circuit having little inductance and critically damped connecting each condenser to its corresponding discharge gap to enable the discharge of the electric energy charged in the condenser through its corresponding discharge gap when the discharge gap is rendered conductive, means for charging each condenser, a plurality of normally ineffective trigger devices, one corresponding to each discharge gap, for rendering the corresponding discharge gaps conductive when effective, and means for rendering the trigger devices effective rapidly in predetermined sequence to render the corresponding discharge gaps conductive rapidly in the said predetermined sequence, thereby to discharge the condensers through their corresponding discharge gaps rapidly in the said predetermined sequence,

' a common resistive load connected in all of the discharge circuits of the discharge gaps, and a ash lamp comprising a pair of electrodes slightly spaced from each other in air and disposed within a closely fitting transparent tube connected to the load and responsive to the discharges of electric energy through the discharge circuits for producing light flashes rapidly in the said predetermined sequence at the single location of the flash lamp.

7. A light-flash-producing-and-recording system having, in combination, a plurality of condensers, a plurality of normally non-conductive discharge gaps through which electric energy may discharge when conductive, one discharge gap corresponding to each condenser, a discharge circuit connecting each condenser to its corresponding discharge gap to enable the discharge of the electric energy charged in the condenser through its corresponding discharge gap when the discharge gap is rendered conductive, means for charging each condenser, a plurality of normally ineffective trigger devices, one corresponding to each discharge gap, for rendering the corresponding discharge gaps conductive when eifective, and means for rendering the trigger devices effective rapidly in predetermined sequence in order to render the corresponding discharge gaps conductive rapidly in the said predetermined sequence, thereby to discharge the condensers through their corresponding discharge gaps rapidly in the said predetermined sequence, a common load connected in all of the discharge circuits of the discharge gaps, a-ash lamp connected to the load and responsive to the discharge of electric energy through the dischargecircuits for producing light ashes rapidly in Sl the vsaid predetermined sequence at a single location, a field .lens for focusing the `light ilazshes iproduced -by the Iflash lamp upon 'la camera len s in lorder to form an -outoli-focus image of the `iiash lamp upon a substantial area of the camera film, `thereby to Aproduce vrapid shadow exposures upon the 'lm in -the fsaid predetermined sequence of an illuminationprodncing object located between the lfield lens and 'the lcamera and focused upon the r`film, and an illumination-sensitive circuit vresponsive to the illumination produced by the object for initiating 'the rendering lelect'ive of the triggerdevices -8. A lli ght-tla'sh-producing system having, in combination, a `plurality of condensers, a vplurality of normally ynon-conduc`tive Ydischarge 'gaps through which electric energy `may "discharge when conductive, one ydischarge Igap corresponding to each condenser, a discharge circuit lconnecting 'each condenser to its corresponding discharge ygap to-en'able the discharge ofthe electric energy charged inthe condenser through `its corresponding discharge gap when the discharge gap is rendered conductive, means for charging each condenser, a plurality of normally inelfectiv'e gaseous-discharge trigger devices, one corresponding 'to each discharge gap, for rendering the corresponding discharge gaps conductive when effective, the trigger devices being interconnected by time-constant-controlled electric 'network means for insuring their operation in predetermined sequence, `'means Vfor initiating the rendering of the trigger devices effective rapidly in predetermined sequence -in order torenderjthe corresponding discharge gaps'conductive rapidly inthe said predetermined sequence, thereby `to disch-'arge the .condensers through their corresponding discharge gaps rapidly in the said predetermined sequence., a common load -connected in all of the discharge circuits ofthe discharge gaps, and a flash lamp connected to the load and responsive to the discharges of electric energy through the discharge circuits for producing light dashes rapidly in the said predetermined sequence at the single location of the ash lamp.

9. A light-flash-producing system having, in combination, a circuit including a first pair of separate condensers and a pair of separate normally non-conductive discharge gaps through which electric energy may discharge when conductive, each discharge gap having a pair of principal electrodes and a trigger electrode, means for simultaneously charging the condensers, a discharge circuit connecting each condenser between the principal electrodes of the corresponding discharge gap, a pair of normally non-conductive gaseous-discharge trigger devices, one corresponding to each discharge gap and each having an anode, a cathode and a control electrode, a second pair of condensers, one connected through a transformer primary winding between the anode and cathode of each trigger device, means for simultaneously charging the second pair of condensers, a pair of secondary transformer windings cooperative with the primary windings, one connected between the trigger electrode and one of the principal electrodes of each discharge gap, means cooperative with the control electrode of one of the trigger devices for rendering the same conductive rapidly to discharge the corresponding condenser of the second pair of condensers between the anode and cathode of the said one trigger device and through the corresponding transformer primary winding, thereby to produce an impulse in the corresponding transformer secondary winding for rendering conductive the corresponding discharge gap and rapidly discharging the corresponding condenser of the lirst pair of condensers therethrough, a time-constantcontrolled electric network connecting the cathode of the said one trigger device to the control electrode of the other trigger device in order to delay the rendering conductive of the other trigger device a predetermined short interval of time after the rendering conductive of the said one trigger device, thereby to delay the rendering conductive of the'other discharge gap and the rapid discharge :therethrough of A'its corresponding condenser of the kfirst pair of condensers the said predetermined short interval of time, a lcommon load connected in the l'discharge circuits of the discharge gaps, and a dash lamp connected kto the load and responsive .to the discharges of electric energy through the discharge circuits for producing a pair-fof rapid light flashes delayed v'by the said predeter -mined short interval of time.

10. A light-tiash-producing lsystem as claimed in claim 9 vand in which lthe Vmeans for charging the rst pair of 'condensers 'is of 'greater voltage than the Ymeans for 'charging thesec'oridvpair Vof condensers, andthe condenser of the first pair of condensers for discharging through the ysaid other discharge gap to produce `the delayed discharge is of greater capacitance than lthat -of the other condenser ofthe said irst pair of condensers.

1l. A `lightashproducing system as claimed in claim 9 and inwhic'h the discharge circuits of the discharge gaps Aare provided vwith resistance suihcient substantially critically 'to damp 'the circuits. 12. A light-'liash-producing system as claimed in claim '9 iand in which the discharge circuits of the second pair of condensers throu-gli'the transformer primary windings are oscillatory and the `'discharge circuits of the discharge gaps are substantially critically damped to produce discharges of thelordei' of a-microsevcond or a fraction thereof, and the time-constant of the said electric network is adjustable to produce delays ofthe order of a few microseconds.

13. Alight-tiashfproducing system as claimed in claim v9 'and in which the lliash lamp Acomprises a pair of rounded 'electrodes slightly 'spaced from each other in air anddisposed Withina closely :iitting 'light-transparent tube.

1.4. A ilight-'iiasheproducing system having, in combination, a plurality of condensers, a plurality of normally non-conductive discharge devices through which electric energy may discharge when conductive, one discharge device corresponding to each condenser and having a pair of principal electrodes and a trigger electrode, a discharge circuit connecting each condenser between the principal electrodes of its corresponding discharge device to enable the discharge of the electric energy charged in the condenser between the principal electrodes of its corresponding discharge device, means for charging each condenser, means for applying successive triggering voltages to the trigger electrodes of the successive discharge devices to render the discharge devices conductive rapidly in predetermined sequence in order to discharge the condensers between the principal electrodes of their corresponding discharge devices rapidly in the said predetermined sequence, and a common ilash lamp having a pair of closely spaced gap electrodes connected to all of the discharge circuits of the discharge devices and responsive to the discharges of electric energy therethrough for producing light flashes rapidly in the said predetermined sequence at the single location of the flash lamp.

15. A light-flash-producing system having, in combination, a plurality of condensers, a plurality of normally non-conductive spark-gap discharge devices through which electric energy may discharge when conductive, one sparkgap discharge device corresponding to each condenser and having a pair of principal electrodes and a trigger electrode, a discharge circuit connecting each condenser between the principal electrodes of its corresponding discharge device to enable the discharge of the electric energy charged in the condenser between the principal electrodes of its corresponding discharge device, means for charging each condenser, means for applying successive triggering voltages to the trigger electrodes of the successive discharge devices to render the discharge devices conductive rapidly in predetermined sequence in order to discharge the condensers between the principal electrodes of their corresponding discharge devices rapidly in the said predetermined sequence, and a common dash lamp connected to all of the discharge circuits of the discharge devices and responsive to the discharges of electric energy therethrough for producing light dashes rapidly in the said predetermined sequence at the single location of the flash lamp.

16. A light-ash-producing system having, in combination, at least a pair of condensers, at least a pair of normally non-conductive discharge devices through which electric energy may discharge when conductive, each discharge device corresponding to one of the condensers and having a pair of principal electrodes and a trigger electrode, a discharge circuit connecting each condenser between the principal electrodes of its corresponding discharge device to enable the discharge of the electric energy charged in the condenser between the principal electrodes of its corresponding discharge device, the discharge circuits sharing a common load impedance, means for charging each condenser, means for applying successive triggering voltages to the trigger electrodes of the successive discharge devices to render the discharge devices conductive rapidly in predetermined sequence in order to discharge the condensers between the principal electrodes of their corresponding discharge devices rapidly in the said predetermined sequence, and a common ash lamp connected with the common load impedance of the discharge circuits of the discharge devices and responsive to the discharges of electric energy therethrough for producing light flashes rapidly in the said predetermined sequence at the single location of the ilash lamp.

17. A light-ilash-producing system having, in combination, at least a pair of condensers, at least a pair of normally non-conductive discharge devices through which electric energy may discharge when conductive, each discharge device corresponding to one of the condensers and having a pair of principal electrodes and a trigger electrode, a discharge circuit connecting each condenser between the principal electrodes of its corresponding discharge device to enable the discharge of the electric energy charged in the condenser between the principal electrodes of its corresponding discharge device, the discharge circuits sharing a common load impedance, means for charging each condenser, means for producing trigger voltages for one of the discharge devices, time-constantcontrolled electric network means connected with the trigger-voltage-producing means for producing further trigger voltages in predetermined sequence after the production of the first-named trigger voltages for the other 0f the discharge devices, means for applying the trigger voltages to the trigger electrodes of the corresponding discharge devices to render them conductive rapidly in succession in order to discharge the condensers between the principal electrodes of their corresponding discharge devices rapidly in the said predetermined sequence, and a common flash lamp connected with the common load impedance of the discharge circuits of the discharge devices and responsive to the discharges of electric energy therethrough for producing light ashes rapidly in the said predetermined sequence at the single location of the flash lamp.

References Cited in the tile of this patent UNITED STATES PATENTS Lord Feb. 6, 1934 Higonnet et al. July 6, 1954 OTHER REFERENCES 

